INFLUENCE OF THE MEASUREMENT CONDITIONS AND THE INITIAL CONTAMINATION OF THE CONCRETE, ON THE POLARIZATION RESISTANCE VALUES MEASURED WITH A GECOR6

Abstract

Rebars corrosion, either induced by carbonation or chlo-ride pollution, is the main source of degradation of rein-forced concrete buildings or bridges. Therefore, corrosionassessment is a crucial input data to establish the adequatelevel of intervention on those structures: maintenance orrepair? If potential or resistivity mappings can give usefulqualitative information about the risk of corrosion, linearpolarization resistance measurements constitute the exclu-sive possibility to evaluate precisely ongoing corrosion.Among the onsite devices available, one of the most used isthe Gecor6©, which is composed of a circular sensorequipped with a series of electrodes (copper/copper-sul-fate for the reference ones, stainless steel for the counter-electrode), including a confinement ring, connected to adata acquisition system. As part of a larger project dedicated to concrete durabilityassessment [1], the purpose of the present study was tocontribute to identify factors influencing electrochemicalon site diagnosis disparities.Two main parameters were considered: the contaminationof the concrete cover and the testing conditions. A series ofpotential, resistivity and LPR measurements was per-formed on 4 reinforced concrete slabs exposed to naturalweathering and presenting distinct initial contamination:reference concrete, endogenous chloride pollution, exoge-nous chloride pollution, and carbonation. For the LPRmeasurements, two parameters were modulated: polariza-tion time and sensor position.The results evidenced a clear impact of the polarisationtime versus the sensor position for the chloride pollutedconcrete, when contrarily the sensor position was the maindisruptive parameter for the carbonated concrete.